1. Field of the Invention
The present application relates to an over-current protection device, and more particularly to an over-current protection device with low resistance.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Because the resistance of conductive composite materials having a positive temperature coefficient (PTC) characteristic is very sensitive to temperature variation, it can be used as the material for current sensing devices, and has been widely applied to over-current protection devices or circuit devices. The resistance of the PTC conductive composite material remains extremely low at normal temperature, so that the circuit or cell can operate normally. However, when an over-current or an over-temperature event occurs in the circuit or cell, the resistance instantaneously increases to a high resistance state (e.g. at least 102Ω), so as to suppress over-current and protect the cell or the circuit device.
According to an over-current protection device design, a PTC material layer is laminated between two electrode layers, and the resistance of the device is dependent on the thickness of the PTC material layer. The thicker the PTC material layer is, the higher resistance the device becomes. Due to the limitation of current manufacturing process, the reduction of thickness is limited to an extent. Therefore, the device will have relatively high resistance, and cannot meet the demand of the large current devices.